The advert was part of a national campaign by Dyson to discredit a rival brandDyson

A Dyson advert comparing one of its vacuum cleaners to a smaller British rival has been banned from ever being shown again after a regulator found it misled customers. The company had run an aggressive national advertising campaign designed to damage the reputation of a successful rival, the Gtech AirRam cleaner.

Sir James Dyson's company produced print adverts and a YouTube video showing what it claimed was the superior performance of its DC59 cordless cleaner compared to Gtech's product. Demonstrating how each cleaner fared when sucking up a spillage of white powder on a wooden floor, Dyson triumphantly claimed its DC59 "has over 10x the suction of Gtech".

But the Advertising Standards Authority (ASA) said the advert was "misleading" and ordered Dyson never to show it again. The ruling on 2 December upheld four complaints from Gtech and accused Dyson of misleading customers. Gtech had complained the adverts "did not reflect normal household cleaning conditions" and "exaggerated the capability of the DC59 to deal with fine dirt".

Following evidence provided by both companies, as well as testing by an independent team, the ASA found Dyson had misled customers by "conflating suction power and pick-up performance". The ASA ruled: "The ads must not appear again in their current form. We told Dyson Ltd to make clear the basis of their comparisons in future and to ensure they held adequate comparative test data to substantiate any implied or stated comparative pick-up performance claims."

Gtech and Dyson go head to head

It comes as Gtech poses a rising threat to Dyson with its range of vacuum cleaners. Founded by designer Nick Grey in 2001, Gtech now reports annual sales of £65 million and has sold over 22m products in 19 countries. It's AirRam costs £199 ($298) compared with Dyson's more expensive DC59 (now called the "Animal"), which is sold for £299 ($448).

Dyson had to counter a market dominated by German rival Bosch when it was founded in 1993. Now dominating the market, it reported annual operating profits of £382m ($572m) in 2013.

A spokesman for Dyson said: "This dispute is over a two-year-old YouTube video which we have happily removed. As guided by the ASA, back to back testing on our latest cordless technology shows our machines possess at least 10 times the suction, and pick up a total of 70% more than the G-tech Air Ram across the three floor types tested."